In the manufacture of semiconductor devices, micro-interconnects are normally formed via formation of a SiO2 or other insulating film by a sputtering apparatus or CVD apparatus and isotropic or anisotropic etching of Si or SiO2 by an etching apparatus. Generally these apparatuses use a plasma discharge to improve film deposition rate and etching performance. For example, a plasma etching apparatus is used as an etching apparatus.
As a dry etching process which uses a plasma etching apparatus, for example, a method is known which uses plasma etching for microfabrication of Si and a dry etching process of various thin films during manufacture of a semiconductor, where the various thin films include an insulating film, electrode film, and wiring film deposited on a substrate.
Plasma etching is performed, for example, as follows. First, plural Si substrates are mounted on a surface of a lower electrode placed in a chamber of a dry etching apparatus, facing an upper electrode. Next, fluorine (F)-based gas such as CF4 or chlorine (Cl)-based gas such as Cl2 is introduced among the mounted substrates and a plasma discharge is induced between the electrodes to generate fluorine-based plasma or chlorine-based plasma. Furthermore, by dry-etching the thin films formed on the substrates with active ions and radicals produced in the generated plasma, the process of plasma etching is finished.
When thin films of GaN, InN, and the like on a substrate are plasma-etched, plasma components and etched material react with each other to produce reaction products such as SiF4 and fluorocarbons. Most of the reaction products are discharged from the chamber in a gaseous state by an exhaust pump, and part of the reaction products is deposited in the chamber in a solid state to form adherent films. Preferably, the adherent films of reaction products are removed.
Thus, a process is known which removes the adherent films by performing dry etching using fluorine-based plasma or chlorine-based plasma and discharging the reaction products (adherent films) adhering to the inside of the chamber out of the chamber. The dry etching, which is intended here to remove the reaction products (adherent films), is performed by generating fluorine-based plasma or chlorine-based plasma under gas conditions different from those for dry etching of the thin films described above.
However, if the reaction products making up the adherent films are fluorocarbon-based etching products, the reaction products do not react properly with fluorine-based plasma or chlorine-based plasma. Thus, the reaction products remain in the chamber. Consequently, if the remaining adherent films peel off and get mixed in the substrate, this could cause pattern defects or reduce yields.
Thus, conventionally, with respect to those parts of the plasma etching apparatus which are irradiated with plasma, including the chamber, a coating with high plasma resistance and corrosion resistance is applied to a surface of a base material to prevent formation of reaction products. As such coatings, an yttrium oxide (Y2O3) coating and aluminum oxide (Al2O3) coating are known. These coatings are effective in curbing generation of reaction products and preventing parts damage caused by plasma attacks.
For example, Patent Document 1 describes a Y2O3 film obtained by heat-treating a Y(OH)3 sol solution applied to a base material, while Patent Document 2 describes an Al2O3 thermally sprayed coating.